U.S. patent application number 11/062420 was filed with the patent office on 2005-10-27 for step and flash imprint lithography.
This patent application is currently assigned to Board of Regents, The University of Texas System. Invention is credited to Colburn, Matthew E., Willson, Carlton Grant.
Application Number | 20050236739 11/062420 |
Document ID | / |
Family ID | 23015492 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050236739 |
Kind Code |
A1 |
Willson, Carlton Grant ; et
al. |
October 27, 2005 |
Step and flash imprint lithography
Abstract
A method of forming a relief image in a structure comprising a
substrate and a transfer layer formed thereon comprises covering
the transfer layer with a polymerizable fluid composition, and then
contacting the polymerizable fluid composition with a mold having a
relief structure formed therein such that the polymerizable fluid
composition fills the relief structure in the mold. The
polymerizable fluid composition is subjected to conditions to
polymerize polymerizable fluid composition and form a solidified
polymeric material therefrom on the transfer layer. The mold is
then separated from the solid polymeric material such that a
replica of the relief structure in the mold is formed in the
solidified polymeric material; and the transfer layer and the
solidified polymeric material are subjected to an environment to
selectively etch the transfer layer relative to the solidified
polymeric material such that a relief image is formed in the
transfer layer.
Inventors: |
Willson, Carlton Grant;
(Austin, TX) ; Colburn, Matthew E.; (Hopewell
Junction, NY) |
Correspondence
Address: |
BOARD OF REGENTS, THE UNIVERSITY OF TEXAS SYSTEM
P.O. BOX 81536
AUSTIN
TX
78708-1536
US
|
Assignee: |
Board of Regents, The University of
Texas System
|
Family ID: |
23015492 |
Appl. No.: |
11/062420 |
Filed: |
February 22, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11062420 |
Feb 22, 2005 |
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10978285 |
Oct 29, 2004 |
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10978285 |
Oct 29, 2004 |
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10806051 |
Mar 22, 2004 |
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10806051 |
Mar 22, 2004 |
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09908765 |
Jul 19, 2001 |
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6719915 |
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09908765 |
Jul 19, 2001 |
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09266663 |
Mar 11, 1999 |
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6334960 |
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Current U.S.
Class: |
264/327 |
Current CPC
Class: |
G03F 7/0002 20130101;
Y10S 977/887 20130101; B29C 43/021 20130101; B29C 2043/025
20130101; B82Y 40/00 20130101; H05K 3/061 20130101; B82Y 10/00
20130101; B29C 43/003 20130101; Y10S 977/897 20130101 |
Class at
Publication: |
264/327 |
International
Class: |
B29C 031/00 |
Goverment Interests
[0002] The U.S. Government has a paid-up license in this invention
and the right in limited circumstances to require the patent owner
to license others on reasonable terms as provided for by the terms
of MDA-972-97-3-0007 awarded by the Defense Advanced Research
Projects Agency (DARPA).
Claims
What is claimed is:
1. A method of forming a layer on a surface, said method
comprising: flowing a polymerizable composition between said
surface and a mold in contact with said polymerizable composition
by providing said polymerizable composition with a viscosity in a
range 0.01 to 100 centipoise at 250 Celsius so that said
polymerizable composition conforms to a shape of said mold;
solidifying said polymerizable composition, defining a solidified
composition; and increasing a distance between said solidified
composition and said mold.
2. The method as recited in claim 1 wherein flowing further
includes providing said polymerizable composition with a viscosity
in a range of 1 to 5 centipoise, inclusive, at 25.degree.
Celsius.
3. The method as recited in claim 1 wherein flowing further
includes applying said polymerizable composition to said surface
and placing said mold proximate to said polymerizable fluid
composition.
4. The method as recited in claim 1 wherein flowing further
includes applying said polymerizable composition to said surface
and pressing a side of said mold into said polymerizable fluid
composition, with said side including a plurality of trenches, with
solidifying further including providing said solidified material
with a pattern complementary to a shape of said side.
5. The method as recited in claim 1 wherein flowing further
includes applying said polymerizable composition to said surface
and pressing a side of said mold into said polymerizable fluid
composition, with said side including a plurality of trenches, and
solidifying further includes providing said solidified material
with a pattern complementary to a shape of said side and further
including providing a substrate having a transfer layer disposed
thereon, with said transfer layer defining said surface, and
transferring said pattern into said transfer layer.
6. The method as recited in claim 5 further including transferring
said pattern into said substrate.
7. A method of forming a layer on a surface, said method
comprising: placing a mold proximate to a surface with a
polymerizable composition being disposed therebetween, said mold
having a side with a plurality of trenches formed therein; flowing
said polymerizable composition between said surface and said mold
to have said polymerizable composition fill said trenches
conforming to a shape of said side by providing said polymerizable
composition with a viscosity in a range 0.01 to 100 centipoise at
250.degree. Celsius; solidifying said polymerizable composition,
defining a solidified composition having a solidified shape
complementary to said shape of said side; and increasing a distance
between said solidified composition and said mold.
8. The method as recited in claim 7 wherein flowing further
includes providing said polymerizable composition with a viscosity
in a range of 1 to 5 centipoise, inclusive, at 25.degree.
Celsius.
9. The method as recited in claim 7 wherein flowing further
includes applying said polymerizable composition to said surface
and pressing said side into said polymerizable fluid
composition.
10. The method as recited in claim 7 wherein flowing further
includes applying said polymerizable composition to said surface
and pressing said side of said mold into said polymerizable fluid
composition, and further including providing a substrate having a
transfer layer disposed thereon, with said transfer layer defining
said surface, and transferring said pattern into said transfer
layer.
11. The method as recited in claim 10 further including
transferring said pattern into said substrate.
12. A composition, comprising: a polymerizable material having a
viscosity in a range of 0.01 to 100 centipoise at 25.degree.
Celsius.
13. The composition as recited in claim 12 wherein said
polymerizable material has a viscosity in a range of 1 to 5
centipoise, inclusive, at 25.degree. Celsius.
14. The composition as recited in claim 12 wherein said
polymerizable material further includes organosilicons.
15. The composition as recited in claim 12 wherein said
polymerizable material further includes silicon-containing material
in an amount greater than about 8 to 10 percent by weight.
16. The composition as recited in claim 12 wherein said
polymerizable composition further includes silicon-containing
materials selected from a set of materials consisting essentially
of silanes, silyl ethers, silyl esters, functionalized siloxanes,
silsesquioxanes.
17. The composition as recited in claim 12 wherein said
polymerizable material further includes components selected from a
set consisting essentially of epoxy groups, ketene acetyl groups,
acrylate groups and methacrylate groups.
18. The composition as recited in claim 12 wherein said
polymerizable material further includes an initiator component to
facilitate solidification of said polymerizable material in
response to predetermined radiation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 10/978,285, filed Oct. 29, 2004, which is a
continuation of U.S. patent application Ser. No. 10/806,051, filed
Mar. 22, 2004, which is a divisional application of U.S. patent
application Ser. No. 09/908,765, now U.S. Pat. No. 6,719,915, which
is a continuation patent application of U.S. patent application
Ser. No. 09/266,663, now U.S. Pat. No. 6,334,960, all having
Carlton Grant Willson and Matthew Earl Colburn listed as
inventors.
FIELD OF THE INVENTION
[0003] The invention generally relates to using lithography
techniques in fabricating various microstructures.
BACKGROUND OF THE INVENTION
[0004] There is currently a strong trend toward fabricating small
structures and downsizing existing structures, which is commonly
referred to as microfabrication. One area in which microfabrication
has had a sizeable impact is in the microelectronic area. In
particular, the downsizing of microelectronic structures has
generally allowed the structures to be less expensive, have higher
performance, exhibit reduced power consumption, and contain more
components for a given dimension relative to conventional
electronic devices. Although microfabrication has been widely
active in the electronics industry, it has also been applied to
other applications, such as biotechnology, optics, mechanical
systems, sensing devices, and reactors.
[0005] Lithographic techniques are often employed in device
microfabrication. See S. Wolf et al., Silicon Processing for the
VLSI Era, Volume 1-Process Technology, (1986), pp. 407-413. Using
microcircuit fabrication as an example, photoresist materials are
applied to a substrate. Next, the resist layer is selectively
exposed to a form of radiation. An exposure tool and mask are often
used to affect the desired selective exposure. Patterns in the
resist are formed when the substrate undergoes a subsequent
"developing" step. The areas of resist remaining after development
protect the substrate regions which they cover. Locations from
which resist has been removed can be subjected to a variety of
additive (e.g., lift-off) or subtractive (e.g., etching) processes
that transfer the pattern onto the substrate surface.
[0006] There is a current move toward developing photolithography
techniques that may allow for forming microscale devices with small
features. Whiteside et al., Agnew. Chem. Int. Ed., 1998, 37, pp.
550-575 propose various techniques. One proposed technique involves
the self-assembly of monolayers. Self-assembled monolayers (SAMs)
typically form spontaneously by chemisorption and self-organization
of functionalized, long-chain organic molecules onto the surfaces
of appropriate substrates. SAMs are usually prepared by immersing a
substrate in a solution containing a ligand that is reactive toward
the surface, or by exposing the substrate to a vapor of the
reactive species. The self-assembly of monolayers is potentially
advantageous in that ordered structures may form rapidly.
[0007] An imprint lithography process that teaches producing
nanostructures with 10 nm feature sizes is proposed by Chou et al.,
Microelectronic Engineering, 35, (1995), pp. 237-240. In
particular, Chou et al. teach pressing a mold having nanostructures
formed therein into a thin resist cast that is present on the
surface of a substrate. The resist cast is designed to conform to
the mold shape. The mold is then removed from the resist cast and
the substrate having the resist cast present thereon is etched such
that the mold pattern is transferred to the substrate.
[0008] Chou et al. teach using (poly)methyl methacrylate for the
resist cast. The use of this material, however, may be
disadvantageous in that it is potentially difficult to form some
structures in varying pattern densities. Moreover, it is perceived
that the etch selectivity may be potentially undesirable for common
microelectronic device processing.
[0009] In view of the above, there is a need in the art for an
imprint lithography process that allows for the formation of
nanostructures having high resolution for a wide range of pattern
densities. It would be particularly desirable if the nanostructures
could be formed in a more efficient manner relative to prior art
processes.
SUMMARY OF THE INVENTION
[0010] The present invention addresses the potential problems of
the prior art, and in one aspect provides a method of forming a
relief image in a structure that comprises a substrate and a
transfer layer formed thereon. The method applies to forming
structures with nanoscale patterns. The method comprises covering
the transfer layer with a polymerizable fluid composition;
contacting the polymerizable fluid composition with a mold having a
relief structure formed therein such that the polymerizable fluid
composition fills the relief structure in the mold; subjecting the
polymerizable fluid composition to conditions to polymerize the
polymerizable fluid composition and to form a solidified polymeric
material therefrom on the transfer layer; separating the mold from
the solidified polymeric material such that a replica of the relief
structure in the mold is formed in the solidified polymeric
material; and finally subjecting the transfer layer and the
solidified polymeric material to an environment that allows for the
selective etching of the transfer layer relative to the solidified
polymeric material such that a relief image is formed in the
transfer layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGS. 1A through 1D illustrate a method for forming a relief
structure in a substrate in accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings and
specification in which preferred embodiments of the invention are
shown. This invention may, however, be embodied in many different
forms and should not be construed as limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. In the
drawings, the thickness of layers and regions are exaggerated for
clarity. Like numbers refer to like elements throughout. It will
also be understood that when a layer is referred to as being "on"
another layer or substrate, it can be directly on the other layer
or substrate, or intervening layers may also be present.
[0013] In one aspect, the invention relates to at least one method
of forming a relief image in a structure comprising a substrate and
a transfer layer formed thereon. The method comprises covering the
transfer layer with a polymerizable fluid composition. The
polymerizable fluid composition is then contacted by a mold having
a relief structure formed therein such that the polymerizable fluid
composition fills the relief structures in the mold. The
polymerizable fluid composition is then subjected to conditions so
as to polymerize the polymerizable fluid composition and to form a
solidified polymeric material therefrom on the transfer layer.
Stated differently, the polymerizable fluid composition becomes
chemically crosslinked or cured so as to form a thermoset material
(i.e., solidified polymeric material). The mold is then separated
from the solidified polymeric material such that a replica of the
relief structure in the mold is formed in the solidified polymeric
material. The transfer layer and the solidified polymeric material
are then subjected to an environment such that the transfer layer
is selectively etched relative to the solidified polymeric
material. As a result, a relief image is formed in the transfer
layer. The method of the invention is advantageous in that a number
of devices may be fabricated therefrom utilizing processes known to
one skilled in the art, such as, but not limited to,
microelectronic devices, information storage devices, printed
wiring boards, flat panel displays, micromachines, and charge
couple devices.
[0014] The substrate used in the above invention may comprise a
number of different materials, such as, but not limited to,
silicon, plastics, gallium arsenide, mercury telluride, and
composites thereof. The transfer layers are formed from materials
known in the art, such as, for example, thermoset polymers,
thermoplastic polymers, polyepoxies, polyamides, polyurethanes,
polycarbonates, polyesters, and combinations thereof. The transfer
layer is fabricated in such a manner so as to possess a continuous,
smooth, relatively defect-free surface that may exhibit excellent
adhesion to the polymerizable fluid. As appreciated by one skilled
in the art, the term "transfer layer" refers to a layer containing
material that may be etched so as to transfer an image to the
underlying substrate from the polymerizable fluid composition as
described in detail herein.
[0015] The polymerizable fluid composition that is polymerized and
solidified in accordance with the methods of the invention
typically comprises a polymerizable material, a diluent, and other
materials employed in polymerizable fluids, such as, but not
limited to, to initiators and other materials. Polymerizable (or
crosslinkable) materials which may be used in the methods of the
invention preferably encompass various silicon-containing materials
that are often present themselves in the forms of polymers. The
silicon-containing materials include, but are not limited to,
silanes, silyl ethers, silyl esters, functionalized siloxanes,
silsesquioxanes, and mixtures thereof. Silicon-containing materials
which are employed preferably are organosilicons. The
silicon-containing materials preferably contain the element silicon
in an amount greater than about 8 percent based on the weight of
the polymerizable fluid composition, and more preferably greater
than about 10 weight percent.
[0016] The polymers which may be present in the polymerizable fluid
composition preferably include various reactive pendant groups.
Examples of pendant groups include, but are not limited to, epoxy
groups, ketene acetyl groups, acrylate groups, methacrylate groups,
and combinations of the above. Although not wishing to be bound by
any theory, it is believed that the polymerizable fluid composition
may react accordingly to a variety of reaction mechanisms, such as,
but not limited to, acid catalysis, free radical catalysis, or 2+2
photocycloaddition.
[0017] The mold used in the methods of the invention may be formed
from various conventional methods. Typically, the materials are
selected such that the mold is transparent which allows the
polymerizable fluid composition covered by the mold to be exposed
to an external radiation source. For example, the mold may comprise
materials, such as, but not limited to, quartz, silicon, organic
polymers, siloxanes polymers, borosilicate glass, fluorocarbon
polymers, metal, and combinations of the above. Preferably, the
mold comprises quartz. To facilitate release of the mold from the
solid polymeric material, the mold may be treated with a surface
modifying agent. Surface modifying agents which may be employed
include those which are known in the art. An example of a surface
modifying agent is a fluorocarbon silylating agent. These surface
modifying agents or release materials my be applied, for example,
from plasma sources, a Chemical Vapor Deposition method (CVD), such
as analogs of paralene, or a treatment involving a solution.
[0018] It should be appreciated that one skilled in the art may
select the substrate, the mold, the polymerizable fluid
composition, the surface modifying agent, as well as any other
materials, such that the method of the invention optimally
functions according to the specific needs of the end user.
[0019] The methods of the invention will now be described in
greater detail to the accompanying drawings in which a preferred
embodiment of the invention is shown. FIG. 1A illustrates a
step-by-step sequence for carrying out the method of the invention.
A structure 30 is present which includes a substrate 10 having a
transfer layer 20 positioned thereon. As shown, a mold 40 is
aligned over transfer layer 20 such that a gap 50 is formed between
mold 40 and transfer layer 20. Mold 40 has a nanoscale relief
structure formed therein having an aspect ratio preferably ranging
from about 0.1 to about 10, and more preferably from about 0.5 to
about 2. Specifically, the relief structures in mold 40 preferably
have a width w.sub.1 ranging from about 10 nm to about 5000 .mu.m.
The relief structures are separated from each other by a distance
d.sub.1, preferably ranging from about 10 nm to about 5000
.mu.m.
[0020] A polymerizable fluid composition 60 then contacts transfer
layer 20 and mold 40 so as to fill gap 50 therebetween, as shown in
FIG. 1B. Polymerizable fluid composition 60 may have a low
viscosity such that it may fill gap 50 in an efficient manner.
Preferably, the viscosity of polymerizable fluid composition 60
ranges from about 0.01 cps to about 1000 cps measured at 25.degree.
C., and more preferably from about 0.01 cps to about 1 cps measured
at this same temperature.
[0021] Referring now to FIG. 1C, mold 40 is then moved closer to
transfer layer 20 to expel excess polymerizable fluid composition
60 such that edges 41a through 41f of mold 40 come into contact
with transfer layer 20. Polymerizable fluid composition 60 is then
exposed to conditions to sufficiently polymerize the fluid.
Preferably, polymerizable fluid composition 60 is exposed to
radiation sufficient to polymerize the fluid composition and to
form a solidified polymeric material, represented by 70 in FIG. 1C.
More specifically, polymerizable fluid composition 60 is exposed to
ultraviolet light, although other means for polymerizing the fluid
may be employed, such as, for example, heat or other forms of
radiation. The selection of a method of initiating the
polymerization of the fluid composition is known to one skilled in
the art, and typically depends on the specific application which is
desired.
[0022] Mold 40 then leaves solidified polymeric material 70 on
transfer layer 20, as shown in FIG. 1D. Transfer layer 20 is then
selectively etched relative to solidified polymeric material 70
such that a relief image 80 corresponding to the image in mold 40
is formed in transfer layer 20. The etching step is depicted in
FIG. 1C. The etching selectivity of transfer layer 20 relative to
solidified polymeric material 70 preferably ranges from about 1.5
to about 100. As an example, the selective etching or the ion
milling may be carried out by subjecting transfer layer 20 and
solidified polymeric material 70 to an environment, such as, but
not limited to, an argon ion stream, an oxygen-containing plasma, a
reactive ion etching gas, a halogen-containing gas, a sulfur
dioxide-containing gas, and combinations of the above.
[0023] Residual material, denoted as 90, which may be in the form
of (1) a portion of polymerizable fluid composition 60; (2) a
portion of solidified polymeric material 70; or (3) combinations of
(1) and (2) might be present in the gaps within in relief image 80.
The method of the invention therefore may further comprise the step
of subjecting residual material 90 to conditions such that residual
material 90 is removed (e.g., a clean-up etch). The clean-up etch
may be carried out using known techniques. Additionally, it should
be appreciated that this step may be carried out during various
stages of the method of the invention. For example, the removal of
the residual material may be carried out prior to the step of
subjecting the transfer layer and the solidified polymeric material
to an environment wherein the transfer layer is selectively etched
relative to the solidified polymeric material. Various environments
may be employed during the clean-up etch, such as, for example,
argon ion milling, fluorine-containing plasma, reactive ion etch
gas, and combinations thereof.
[0024] In the drawings and specification, there have been disclosed
typical preferred embodiments of the invention, and although
specific terms are employed, they are used in a generic and
descriptive sense only and not for the purposes of limitation. The
scope of the invention being set forth in the following claims.
* * * * *